Biggest tires for a unholy rolling darryl rim??

Hi all!
long time reader, first time poster. I'm about to purchase a mukluk 3, but straight off the bat I want bigger tires..... So what fits onto the unholy rolling darryl and fits the frame that's bigger than the surly Nate? Or should I just shut up and go with the Nate? I saw the husker dŁ is a 4.0 tire is this a better option?
Thoughts and opinions are all welcome!